Spray booth



Jan. 28, 1969- D. J. PEEPS ET AL 3,424;129

SPRAY BOOTH Filed April 20, 1967 Sheet of 4 INVENTORS. pal/4w J @595 a?Lav/5 M Un [A/ BY 8 pm V, AIME/V6745.

Jan. 28, 1969, DJ. PEEPS E AL 3,424,129 I SPRAY BOOTH I Filed April20,1967 Sheet a of 4 INYVENTORSJ fiat 4m J @4 56? [5/145 M One/v Jan.28,1969 D. J. PEEPS ET AL 3,424,129

I SPRAY ,BOOTH Filed April 20. 1967 Sheet 3 of 4 47' ram/5r:-

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SPRAY BOOTH Filed April 20,. 1967 Sheet 4 of 4 L i a 1 4' AZ "4' 51 1? ZUnited States Patent 3,424,129 SPRAY BOOTH Donald J. Peeps, Rossford,and Lewis M. Owen, Toledo,

Ohio, assignors to The DeVilbiss Company, Toledo Ohio, a corporation ofOhio Filed Apr. 20, 1967, Ser. No. 632,297

US. Cl. 118-314 14 Claims Int. Cl. B05c 11/16, 5/00 ABSTRACT OF THEDISCLOSURE A spray booth is provided in which air is directed into thebooth primarily around the spray heads and is exhausted from the boothat a remote location. "Flow of air is thus established toward thearticle being coated with little turbulence and air is supplied where itis needed the most, thereby minimizing air requirements for the spraybooth. The equipment, including spray heads, reciprocators, and controlsare not located directly in the coating chamber and are not subject tospray backlash, thereby reducing cleaning and increasing operating time.The oporator is similarly situated, eliminating the requirement forusing a respirator and reducing possible hazard to him. 'IIhe sprayheads are sometimes moved toward and away from the coating chamber inorder to accommodate articles of different sizes. In such an instance,the spray booth also has means to maintain the position of entry of theair constant relative to the spray heads.

This invention relates to spray apparatus for coating articles andspecifically to a spray booth using much less air than is commonlyrequired and in which air is directed with little turbulence around thespray heads and toward the articles.

In a spray booth, the principal reason for moving air therethromgh andexhausting air therefrom is to maintain sprayed coating materialparticles in the air below an explosive concentration; the airrequirements for this purpose are relatively small. However, much higherair volume has been needed in spray booths to protect the operatortherein. Consequently, the air volume requirements in a spray boothcould be reduced substantially if the operator were situated in aseparate area or chamber substantially free of sprayed particles.Similarly, spray booths require relatively high volume to carry awayoverspray and prevent spray backlash onto the coating materialequipment, which causes frequent shutdowns and cleaning. The high aidvolume again could be substantially reduced if such equipment werepositioned similarly to the operator.

In accordance with the invention, it has been found that a spray boothcan be divided into two chambers with a wall therebetween located nearthe spray heads and having an inlet opening around the spray heads fordirecting air past the spray heads and toward the article being coated.The air can then be exhausted from the spray booth at a location remotefrom the spray heads and the inlet opening in order to direct the airwhere it is needed the most and to minimize turbulence in the air flow.The operator as well as the spray head reciprocators, controls, andrelated components are then located in the spray booth on the side ofthe wall opposite the article being coated. The air entering the openingaround the spray heads can move at relatively high velocity, even thoughof relatively low volume, because of the restricted size of the opening.This velocity virtually eliminates any possibility of overspray comingback through the opening and into contact with the operator or the sprayapplicator components. Hence, with the use of relatively low volume air,the operator and the components are protected from "ice overspray. Afterthe air passes through the restricted opening into the coating chamber,it can disperse so that its velocity drops substantially. In thismanner, the spray particles are not carried at relatively high velocityto the article being coated, in which case a substantial part of theparticles is carried past the article as overspray.

The substantial reduction of air requirements enables a substantialreduction in the size of blowers and ducts employed, which reduces theirinitial as well as operating costs. Further, the air supply to spraybooths is heated, particularly for operator comfort, and the cost ofheating is often a substantial cost in the overall operation of spraybooths. By substantially reducing the air requirements to the spraybooth, heating cost of the air is also substantially reduced.

In some applications, the spray heads are moved toward and away from thecenter of the booth as the size of the articles being coated varies inthickness. Thus, the spray heads are moved back from the booth centerfor thicker articles and forwardly into the booth for thinner articles.In such an instance, the relationship of the spray heads to the inletopening through which air is supplied into the chamber will vary andchange the air flow characteristics around the spray heads. To maintainthe air flow characteristics constant and uniform with respect to thespray heads, the present invention provides walls or shrouds forming arelatively narrow air inlet around the spray heads and arranged to movewith the spray heads as they are moved into and out of the chamber. Awall defining part of the coating chamber is provided with a passagewhich cooperates with the shroud so that substantially no air can passbetween the passage walls and the shroud. In this manner, all of the airflowing into the chamber passes around the spray heads in a constantpattern, regardless of the position of the spray heads relative to thearticle being coated, to maintain constant air flow characteristicsrelative to the spray heads.

It is, therefore, a principal object of the invention to provide a spraybooth which requires a substantially lower volume of air thanheretofore, resulting in a substantially lower operating cost.

Another object of the invention is to provide a spray booth having meansfor directing air entering a coating material chamber thereof past thespray heads and toward the workpiece in a non-turbulent manner.

A further object of the invention is to provide a spray booth having acoating material chamber and an air supply chamber for an operator andspray components with a restricted opening between the chambers throughwhich air and coating material particles are supplied to the coatingmaterial chamber, thereby reducing contamination of the coating materialcomponents by overspray.

Yet another object of the invention is to provide a spray booth havingspray heads movable toward and away from a coating material chamber, andhaving means for directing substantially constant flow of air past thespray heads toward the article, regardless of the position of the sprayheads relative to the article.

Other objects and advantages of the invention will be apparent from thefollowing detailed description of preferred embodiments thereof,reference being made to the accompanying drawings, in which:

FIG. 1 is a perspective view, wth parts broken away, of a spray boothembodying the invention;

FIG. 2 is a view in vertical, transverse cross section of the spraybooth of FIG. 1;

FIG. .3 is a view in horizontal cross section of the spray booth ofFIGS. 1 and 2;

FIG. 4 is a slightly enlarged, detailed view of part of the sprayapparatus of FIG. 3;

FIG. 5 is a fragmentary view in horizontal cross section of a modifiedspray booth; and

FIG. 6 is a view on horizontal cross section of modified spray apparatusand air inlet openings.

A spray booth according to the invention is indicated at 10 and includesa central coating material chamber 12, preferably somewhat wider thanthe widest article expected to be coated therein. The spray booth can beused with an overhead conveyor 14- to provide a semicontinuousoperation, the conveyor extending centrally longitudinally through thechamber 12. While the conveyor 14 is shown as being overhead, a floorconveyor may be used. In either case, the article is preferably groundedelectrically through its support when electrostatic coating is employed.The length of the chamber 12 depends in part on the coating operations.For example, for an automobile body, a first part of the length of thechamber can be used to coat the sides of the body, a second part can beused to coat the top, hood, and trunk lid, and a third part employed fortouch-up work.

The principles of the invention also apply to any conventional spraybooth in which articles are moved into the chamber through a sideopening, coated, and removed through the same opening. However, the useof the invention in connection with a continuous type booth in whichopenings are provided at both ends for the ingress and egress ofarticles is particularly advantageous. With air applied directly at thelocation where it is neeeded, around the spray heads, and directedtoward the articles being coated, air that enters through the end wallarticle openings does not seriously interfere with the coating process.

A relatively high velocity is only needed at the restricted openingaround the spray heads rather than across the entire spray booth as hasheretofore been necessary. The air can disperse after entering thecoating material chamber through the restricted opening and thereby slowdown substantially. Consequently, there is no high velocity air carryingthe coating material particles to and past the article being coatedwhich tends to increase overspray. The high velocity air only at thespray head opening is sufficient to prevent backlash of coatingmaterialparticles to the spray heads and into the air supply chamberwhere they could contaminate the coating material apparatus and be ahazard to the operator. Since a substantially lower volume of air isrequired for spray booth, only a sufiicient amount to provide thenecessary velocity through the opening, the ductwork and fans or blowersemployed can be substantially reduced in size. This results in both alower initial cost and lower operating cost. Further, the cost ofheating the air, which is a substantial factor, especially in colderclimates, is also correspondingly reduced.

The substantial reduction in air volume achieveable with the use of theinvention is illustrated by an example of a conventional spray booth. Inthe spray booth, which measures 12 feet by 12 feet, an air volume of14,400 c.f.m. was required to attain an air velocity of 100 f.p.m. inthe booth. While a much lower velocity could have been employed tomaintain the concentration of volatile coating material particles belowan explosive level, the higher velocity was necessary to carry off theoverspray and prevent excessive contamination of the coating equipmentand undue hazard to the operator. A wall was then installed dividing thespray booth into a coating material chamber in which the articles werecoated and an air supply chamber containing the coating materialcomponents and the operator, and an opening measuring 2 feet 6 incheswide by 12 feet high was made in the wall around the spray heads. Withthis opening, an air volume of only 3300 c.f.m. was required to achievean air velocity of 110 f.p.m. through the opening. This velocity wassufiicient to prevent coating material particles entering the openinginto the air supply chamber and yet the air dispersed after passingthrough the restricted opening so as not to carry the coating materialparticles at an excessive speed toward and past the articles beingcoated.

By way of another example, in one 40 foot long continuous booth, 90,000c.f.m. of air was previously required to assure an adequate flow. Thiscontinuous booth was used to coat automobile bodies and a 10 footsection at the exit end was employed to touch-up the bodies. When thesystem according to the invention was employed in this booth, the airrequirement was reduced to only 36,000 c.f.m. and could have been lowerexcept for the fact that the conventional air exhaust system was stillemployed in the touch-up area, constituting about onefourth of theboothlength.

An article designated A can be carried through the chamber 12 on hangers16 suspended from the conveyor 14 with the articles moving into thechamber through an opening 18 (FIG. 3) and out of the chamber through anopening 20, each of which openings can be adjustable with sliding doorsto maintain the openings as small as possible for the width of theparticular article being coated.

Both sides of the article can be coated by spray units 22 which includecoating or spray heads 24 mounted on a suitable supporting post or stem26, with the spray heads supplied with coating material from a containerwhich can be located away from the spray area. The stem 26 is preferablyreciprocated to assure uniform coating of a large article from theplurality of spray heads. A suitable reciprocator may be disposed in ahousing 28. The entire unit including the spray heads, supporting frame,and the reciprocator housing can be mounted on a carriage 30 havingwheels 32 movable on tracks 34. This enables the spray heads to be movedin and out with respect to the chamber 12 to maintain a given distancebetween the spray heads and the adjacent surfaces of the articles beingcoated. The spray heads may also be moved in and out for each articlebeing coated, if the width thereof varies from one end to the other. Aremote power supply (not shown) is provided to establish anelectrostatic field adjacent the spray heads, in a known manner.

The spray units 22, each comprising a bank of spray guns and theiroperating mechanism, are located in virtually separate outer, air supplychambers 36 on each side of the coating chamber 12 and separatedtherefrom by sidewalls or partitions 38. Air for the coating chamber 12is supplied through the chambers 36, in this instance, from outside thebuilding in which the spray booth is located. For this purpose, a mainsupply duct 40 is connected to two branch ducts 42, which communicatewith the supply chambers 36, with the main duct 40 having an inletoutside the building. A heater 44 and a suitable supply blower 46 arelocated in the main duct 42 for supplying and-Warming the outside air.

The air from the supply chamber 36 passes into the coating materialchamber 12 through restricted openings designated 48 formed in thepartition or wall 38, with side edges of the openings 48 being definedby side plates 50. The volume of air need be only enough to establish avelocity through the openings 48 sufiicient to prevent deposit ofcoating material particles onto the spray heads 24 or the relatedcomponents in the supply chamber 36. The necessary air flow in thecoating material chamber for preventing coating apparatus contaminationand hazard to the operator will then be much closer to that required tomaintain the concentration below the minimum explosion level.

In order to maintain the air flow characteristics constant around thespray heads 24, regardless of their position, a shroud or inlet 52formed by inwardly directed plates or walls 54 is mounted on each of thecarriages 30 and movable therewith. As shown particularly in FIG. 4,outer peripheral edge portions 56 of the plates 54 extend close to theside plates 50 so that substantially no air will pass therebetween.Inner edges 58 of the shroud plates 54 form an opening of constant areaaround the spray heads 24 so that the area of this opening and therelationship of the opening to the spray heads remains constantregardless of the position of the spray heads.

In order to maintain a smooth flow of air and reduce turbulence to aminimum, the air is exhausted from the chamber 12 at a location remotefrom the inlet openings 48. In the form of the booth shown, exhaustopenings for the air from the booth are provided in the floor of thecoating chamber 12 by grating 60. The exhaust openings can be locatedacross the entire floor or only a portion thereof on the side of thechamber spaced from the spray heads. The air exhausted through thegrating can be pulled through lower exhaust chambers or water tanks 62and upwardly through vertical exhaust ducts 64 having headers 66 byexhaust fans 68. Water is sprayed from the headers 66 over bafiles 67 toclean the air as it flows through the exhaust ducts 64. As shown, theexhaust ducts are located in the supply chambers 36, at spaced portionsthereof. The chambers 36 also have access doors 70 for an operator whocan work in the chambers 36 without hazard from the coating materialparticles which are kept entirely out of the chambers.

In one form, the capacity of the exhaust fans 68 is slightly less thanthe capacity of the supply fans or blowers 46 so that a slight positivepressure will be maintained in the chamber 12, thereby preventing theflow of air-borne particles, such as dust, into the chamber 12 throughthe end openings 18 and 20.

While the exhaust openings in the form shown are located in the floor ofthe chamber 12, the exhaust openings can also be located in the sidewalldirectly opposite the spray heads so that the flow of air in such aninstance is across the booth and around the articles. In either case,the exhaust openings are remote from the inlets to provide a smooth flowof air and maintain minimum turbulence in the chamber. When the sprayheads and air inlets are located overhead, as adjacent a topcoatingdevice, the exhaust openings again can be in the floor, as shown, or inlower portions of the sidewalls of the coating chamber. Further, whilethe spray heads are shown as being mechanically manipulated, they canalso be manually manipulated by an operator in the supply chamber 36.

A slightly modified spray booth 72 is partly shown in FIG. 5. This boothagain is of the continuous type with a suitable conveyor for carryingarticles A therethrough. In this instance, the articles A, to be coatedon both sides again, do not vary more than a few inches in thickness.Consequently, spray heads 74 are supported on stationary controlhousings 76. The spray heads can reciprocate but need not move in andout with respect to the workpiece.

In this instance, the spray booth apparatus is located in an existingenclosed area or room designated 78 which can be provided with a forcedsupply of air by fans 80 if desired, although this is not essential ifthe room is of sufficient size and has sufficient openings. As with thebooth 10, walls or bafiles 82 divide the spray booth into coatingmaterial chambers 84 and air supply chambers 86. All of the air for thecoating material chambers is thereby supplied through inlet openingsindicated at 88 having side plates 89 directing the air inwardly. Aswith the previous spray booth, the air in this instance flows atrelatively high velocity through the openings 88 so that a relativelysmall volume of air will provides sufiicient velocity to prevent coatingmaterial backlash. The control housings 76 and similar components willremain uncontamina-ted and an operator can be in or adjacent the supplychambers 86 without hazard.

The air is exhausted from locations spaced from the inlet openings 88,with the air flowing from the inlets to the exhaust outlets past thearticles A. In this instance, the outlets are provided by a plurality ofbafiies 90 through which the air travels by a circuitous route toexhaust ducts 91 which are equipped with the usual exhaust blowers (notshown).

Frequently, the flow of air in a spray booth will change over a periodof time as conditions change, e.g. the filters becoming partiallyclogged, etc. In such an instance, the pressure differential between theair supply and coating material chambers may vary and change the flowpattern. To minimize this variation and also to supply some additionalair between the articles A, louvers 92 can be employed in the sidewalls82, located adjacent the inlet opening 88 in this instance. The airthrough the louvers 92 helps balance pressure differential between thechambers by increasing air flow into the coating chamber as the pressuredifferential increases, and vice versa. The louvers also reduce anytendency for the overspray to be deposited on articles adjacent the onebeing coated.

It will be seen that the spray booth 72 of FIG. 5 differs from theprevious one in several respects. The spray heads 74 are stationary inthis instance. The air supply chambers 86 do not have a direct supply ofair. The air is exhausted from the opposite sidewall of the spray booth.Finally, the control louvers are employed to balance and influence airflow.

Referring to FIG. 6, a slightly modified spray device is shown. In thisinstance, spray heads 94 are mounted in two banks on posts or stems 96which are connected by a cross bar 98 to structural members 100 and ahousing 102. The housing 102 in this instance is mounted by means of acarriage 104 on tracks 106 for movement toward and away from theworkpiece. Where the banks of spray heads 94 are spaced apart more thanabout four feet, an inlet opening generally designated 108 is equippedwith a central bafile or wall 110 blocking space in the opening 108between the banks of the spray heads 94. The bafiie 110 can be mountedon a shroud 112 encompassing both banks of spray heads and having sideplates 114 cooperating with side plates 116 adjacent the edges of theopening 108. The spray heads and shroud can be partially suspended by anoverhead trolley, in this instance, and move in and out with thecarriage 104. Particularly if the control housing 102 and the sprayheads 94 are stationary, the shroud 112 and the baffle 110 can bestationary with respect to the opening 108.

Various modifications of the above described embodiments of theinvention will be apparent to those skilled in the art, and it is to beunderstood that such modifications can be made without departing fromthe scope of the invention, if they are within the spirit and the tenorof the accompanying claims.

We claim:

1. Apparatus for aiding in coating articles comprising means forming acoating chamber, a support in said chamber for an article to be coated,means forming an air supply chamber, a wall common to the coatingchamber and said air supply chamber having an air inlet opening thereinbetween said air supply chamber and said coating chamber to direct airfrom said air supply chamber to said coating chamber, a spray headadjacent said inlet opening for directing coating material particlestoward the article, a shroud having an opening therein positioned aroundsaid spray head and mounted in said inlet opening in a predeterminedposition relative to said spray head for directing air from said airsupply chamber through said shroud past said spray head, and means forexhausting air from said coating chamber at a location remote from saidinlet opening so that the coating material particles and the air travelin the same general direction across said coating chamber to minimizeturbulence as the air flows through said coating chamber from said inletopening around said spray head and to the exhaust.

2. Apparatus according to claim 1 wherein said exhaust means is locatedin the floor of the coating chamber.

3. Apparatus according to claim 1 wherein said article supporting meanssupports said article at least partly in the path of the air flowingfrom said air inlet opening to said exhaust means.

4. Apparatus according to claim 1 characterized further by said airsupply chamber being enclosed on all sides and having access means bywhich an operator can enter said air supply chamber.

5. Apparatus according to claim 1 characterized further by said shroudhaving an additional opening therein between the coating chamber and theair supply chamber, and an additional spray head in said additionalopening.

6. Apparatus according to claim 1 characterized further by air supplymeans communicating between said air supply chamber and ambient, outsideair for supplying outside air directly to said air supply chamber.

7. Apparatus for aiding in coating articles, said apparatus comprisingmeans forming a coating chamber, a support in said chamber forsupporting an article to be coated, a spray head, a carriage supportingsaid spray head for movement toward and away from the article, a wallcommon to said coating chamber and an air supply chamber, said wallhaving an opening between said chambers, means associated with saidopening and forming a passage in the direction of the path of movementof said carriage, and means on said carriage and movable therewith insaid passage forming an air inlet around said spray head.

8. Apparatus according to claim 7 characterized by said air inletforming means extending close to said passage means so that air flowbetween said supply chamber and said coating chamber is substantiallyrestricted to the air inlet around said spray head for any operatingposition of said carriage relative to the article.

9. Apparatus according to claim 8 wherein said passage means has alength at least equal to the length of the path of said carriage.

10. Apparatus according to claim 8 wherein said air inlet means on saidcarriage comprises slanted wall means, the outer edges of which extendclosely to said passage means and the inner edges of which form theinlet opening to direct the air inwardly toward the path of particlesissuing from the spray heads.

11. Apparatus according to claim 8 wherein said passage is formed byparallel plates affixed to said wall and said air inlet forming meanscomprises ashroud formed partially around said spray head and being oftruncated conical shape in horizontal cross section with the outer edgesof the shroud disposed closely adjacent said plates for all positions ofsaid spray head.

12. Apparatus according to claim 7 characterized further by meansforming an air exhaust opening spaced remotely from said air inlet.

13. Apparatus according to claim 7 characterized further by said inletforming means having an additional inlet opening between said coatingchamber and said air supply chamber, an additional spray head in saidadditional inlet opening.

14. Apparatus according to claim 7 characterized further by said airsupply chamber being enclosed on all sides and having access means bywhich an operator can enter said air supply chamber.

References Cited UNITED STATES PATENTS 2,230,646 2/41 Klausmeyer.

2,445,074 7/48 McCue.

3,170,384 2/65 Krantz et al. 98l15 X 3,270,711 9/66 Leach 118326 X3,279,421 10/66 Tilney et al. 118-323 X WALTER A. SCHEEL, PrimaryExaminer.

J. P. MCINTOSH, Assistant Examiner.

U.S. Cl. X.R.

